Readily available and modular concrete masonry units (CMUs) are commonly used for constructing low-rise buildings (i.e., typically less than three stories). These buildings include residential, educational, commercial, and industrial structures. The CMUs are held together with mortar thereby forming a rigid structure. Many of the CMUs have hollow cores that are used to create cavity walls, wherein steel reinforcement can be placed in the vertical and horizontal spaces to carry loads and resist other forces acting upon the walls. Structural support to walls and footings may be required by structural engineers or architects to meet local building codes. The building codes vary in different geographic regions in association with potential lateral loads to walls resulting from wind or earthquake motions from seismic activity.
Structural reinforcement of hollow core wall units typically relies on placing steel reinforcing bar (rebar) in wall units that are connected to rebar in the footing and subsequently filling the cores with grout. The current disclosure provides alternative methods and devices that have significant advantages over the use of rebar for reinforcement of walls in low-rise buildings. Specifically, apparatus and methods are used to construct a concrete footing reinforced with wire rope that is continuously connected to a wall composed of hollow core units built in courses on top of the reinforced footing, in which selected hollow cores have straightened and connected wire rope vertically within vertical cores, and selected bond beam blocks have straightened and connected wire rope horizontally within hollow cores, and the cores that contain straightened and connected wire rope are filled with grout to form a reinforced structural wall that is interconnected with the concrete footing.
Other building materials, such modular hardscape units, also have hollow cores that could benefit from the apparatus and methods presented in the current disclosure. The reference to hollow core wall units used in the context of the current disclosure is, therefore, not limited to CMUs, but any modular wall units or masonry blocks that have holes, channels, or hollow cores through which wire rope could be placed, continuously connected to a concrete footing also reinforced with wire rope using the apparatus and methods described herein, and thereby form a structural wall that is interconnected with a reinforced footing.
There are advantages of using the wire rope apparatus and methods described in the current disclosure compared to the conventional use of rebar in structural walls. A common practice is to extend rebar upward from foundations or footings and for masons to lift heavy blocks up and over the rebar. Although protective caps are made for the top of the vertically exposed rebar, only those caps that contain metal can minimize the risks of serious injury or even death from workers falling on rebar. Even though falls at construction sites are the most common form of accidents according to the Occupational Health and Safety Association (OSHA), construction workers often neglect using protective caps on rebar, or use improper caps. OSHA reports indicate that serious injuries have resulted from workers falling on rebar in addition to death by impalement. Other serious accidents occur while working with rebar, such as cutting or bending the rebar.
Worker injuries also can result from the repetitive lifting of masonry blocks, particularly for sections of walls with extended lengths of rebar and when larger CMUs are involved (e.g., a two-core cement block with nominal dimensions of 8 by 12 by 16 inches weighs about 40 pounds). The use of wire rope for structural support reduces the potential for these types of accidents since wire rope does not stand upright or protrude laterally like rebar, and the amount of block lifting is limited to the height of the current wall course that is being worked on (i.e., no lifting blocks up and over the vertically exposed rebar). Another key advantage over rebar is that wire rope does not have to be bent and is flexible enough to go around obstructions in the footing and/or wall cores, saving workers time and therefore project costs.
There are also practical reasons that masons prefer not to lift blocks up and over rebar that extends vertically above a footing, sometimes at substantial heights of 10 or 15 feet. Considerable time is required to lift the blocks up and over the vertically extended rebar, breakage of blocks is common in this process, and it is also difficult to keep mortar on the block edges during the extensive lifting process. These practical limitations are often overcome by overlapping (or splicing) two shorter segments of rebar together to create a single structural integrity. Wire tying of rebar overlap will likely be specified by the structural engineer or architect in accordance with Section 2107 of the International Building Code.
However, since building inspectors are not available to observe every reinforced hollow core, some masons are known to take short cuts to avoid the time it takes to properly overlap and tie rebar together. Rebar that is simply stuck in a core and may not be close to another section of rebar, and/or has insufficient overlap, defeats the purpose of continuous reinforcement (i.e., to resist lateral loads to a wall from wind or seismic forces that could cause a wall to be damaged or potentially fail). Unfortunately, improper installations of rebar will be hidden from inspectors once the next course of wall units is laid and the cores are grouted.
Coiled wire rope is significantly safer to work than rigid rebar in the proposed application since it can be conveniently stored in the hollow cores as additional courses are laid. Workers can simply pull the coils of wire rope upward as the wall progresses without it interfering with the masonry activities. Building inspectors and project supervisors will be in a better position to observe with only periodic checks that continuous reinforcement of the wall is provided through the use of wire rope. Apparatus in the current disclosure allow additional strands of wire rope to be joined vertically and horizontally in a straightforward and continuous manner that can also serve as convenient inspection points for building inspectors and supervisors without significant delays in the masonry activities.
The apparatus and methods in the current disclosure have applications beyond the use for structural walls and foundations described herein. For example, other construction applications include, but are not limited to, reinforcement of concrete floor slabs, structural support of retaining walls and free-standing hardscape walls, and reinforcement between footings or slabs with overlying wooden or metal frame structures. The devices described in the current disclosure also have applications beyond the use for interconnected foundations and structural walls, some of which are described herein; other uses others will become apparent to future users when the products are commercialized.